Programming the Shape Transformation of Composite Hydrogel Sheet via Erasable and Rewritable Nanoparticle Patterns.

Hydrogels with shapes that can be adapted to environment have attracted great attention from both academic and industrial community. We report herein a new and robust strategy to reprogram the light-induced shape transformation of thermo-responsive composite hydrogel sheet with erasable and rewritable patterns of iron oxide nanoparticles as photothermal agents. Numerous distinct and reversible shape transformations are achieved from a single hydrogel sheet by repeatably writing in the sheet with different nanoparticle patterns. The shape transformations were verified by finite element modeling. The present strategy is simple, fast and efficient in reprogramming shape change of thermo-responsive hydrogel material. The composite hydrogel sheet may find applications in soft robotics, tissue engineering and controlled release.